The University of Toronto accepts Letters of Reference electronically as part of the online application. U of T will invite your referees to submit a reference via e-mail using the information provided.
If you are trying to use a free email address (yahoo, gmail, etc.) it will not be accepted and the box must be left blank. If you leave the email box blank, you must request your references directly. Request that your referees enclose the letter of reference in a sealed envelope with their signature across the seal. It is your responsibility to forward the reference letters to the graduate unit by the deadlines posted online. Some departments provide specific templates for references; please check the Supporting Documents page of your application for instructions.